title: A purine analog synergizes with chloroquine (CQ) by targeting Plasmodium falciparum Hsp90 (PfHsp90).
abstract: BACKGROUND
  Drug resistance, absence of an effective vaccine, and inadequate public health measures are major impediments to controlling Plasmodium falciparum malaria worldwide. The development of antimalarials to which resistance is less likely is paramount. To this end, we have exploited the chaperone function of P. falciparum Hsp90 (PfHsp90) that serves to facilitate the expression of resistance determinants.
  
  
  METHODS
  The affinity and activity of a purine analogue Hsp90 inhibitor (PU-H71) on PfHsp90 was determined using surface plasmon resonance (SPR) studies and an ATPase activity assay, respectively. In vitro, antimalarial activity was quantified using flow cytometry. Interactors of PfHsp90 were determined by LC-MS/MS. In vivo studies were conducted using the Plasmodium berghei infection mouse model.
  
  
  RESULTS
  PU-H71 exhibited antimalarial activity in the nanomolar range, displayed synergistic activity with chloroquine in vitro. Affinity studies reveal that the PfHsp90 interacts either directly or indirectly with the P. falciparum chloroquine resistance transporter (PfCRT) responsible for chloroquine resistance. PU-H71 synergized with chloroquine in the P.berghei mouse model of malaria to reduce parasitemia and improve survival.
  
  
  CONCLUSIONS
  We propose that the interaction of PfHsp90 with PfCRT may account for the observed antimalarial synergy and that PU-H71 is an effective adjunct for combination therapy.
authors.affiliation: Department of Laboratory Medicine & Pathobiology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Dea
authors.initials: D
authors.lastname: Shahinas
authors.forename: Asongna
authors.initials: A
authors.lastname: Folefoc
authors.forename: Tony
authors.initials: T
authors.lastname: Taldone
authors.forename: Gabriela
authors.initials: G
authors.lastname: Chiosis
authors.forename: Ian
authors.initials: I
authors.lastname: Crandall
authors.forename: Dylan R
authors.initials: DR
authors.lastname: Pillai
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000962:Antimalarials / Q000378:metabolism / Q000494:pharmacology*; D052117:Benzodioxoles / Q000378:metabolism / Q000494:pharmacology*; D002738:Chloroquine / Q000378:metabolism / Q000494:pharmacology*; D002853:Chromatography, Liquid; D004357:Drug Synergism; D005434:Flow Cytometry; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D008288:Malaria / Q000517:prevention & control*; D051379:Mice; D010963:Plasmodium falciparum / Q000187:drug effects / Q000378:metabolism*; D011687:Purines / Q000378:metabolism / Q000494:pharmacology*; D020349:Surface Plasmon Resonance; D053719:Tandem Mass Spectrometry
chemical_list: D000962:Antimalarials; D052117:Benzodioxoles; D018841:HSP90 Heat-Shock Proteins; D011687:Purines; C526550:9H-purine-9-propanamine, 6-amino-8-((6-iodo-1,3-benzodioxol-5-yl)thio)-N-(1-methylethyl)-; D002738:Chloroquine; D000251:Adenosine Triphosphatases